In a small cell enhancement scheme involved in for example the 3rd Generation Partnership Project (3GPP), an important aim is to use a high-order modulation scheme (for example, 256 Quadrature Amplitude Modulation (QAM)) in downlink transmission to improve spectrum efficiency. In order to support the 256 QAM downlink transmission in a conventional system, it is necessary to redesign a Channel Quality Indicator (CQI) table, for example, by deleting several Quadrature Phase Shift Keying (QPSK) indices, adding several new 256 QAM indices, and keeping the size of the CQI table unchanged.
With this modification, the range of modulation order of the CQI table is extended, while the size of the table is unchanged, which would result in degraded accuracy of the CQI table. It is conceivable that, with development of communication technology and physical devices, higher modulation order will be implemented and introduced into existing systems. If the method in the 3GPP is still adopted to modify the CQI table by deleting some original indices and adding some new indices, the accuracy of the CQI table will becoming lower and lower, which may lead to a degradation of system performance.